1. Field of the Invention
The present invention relates to a pattern exposure method, a conductive film producing method, and a conductive film, particularly to a pattern exposure method containing proximity-exposing a photosensitive material in a periodic pattern, a conductive film producing method using the pattern exposure method, and a conductive film.
2. Description of the Related Art
In recent years, conductive films obtained by various production methods have been studied. Among them, a silver salt-type conductive film is produced by pattern-exposing an applied silver halide emulsion to form a conductive silver portion for ensuring a conductivity and an opening portion for ensuring a transparency (see, e.g. Japanese Laid-Open Patent Publication Nos. 2004-221564 and 2004-221565). In a known method for producing the silver salt-type conductive film, a photosensitive material is continuously conveyed, subjected to a proximity exposure through a photomask disposed with a proximity gap of 500 μm or less with respect to the photosensitive material, and thereby exposed in the mask pattern periodically in the conveying direction (see, e.g. Japanese Laid-Open Patent Publication Nos. 2007-072171 and 2007-102200). Also, a conductive film produced by a printing method is known (see, e.g. Japanese Laid-Open Patent Publication No. 2008-283042).
In above Japanese Laid-Open Patent Publication No. 2007-072171, a simulation of proximity gap change within a range of 50 to 550 μm is performed to study the relation between the proximity gap and light intensity distribution generated due to optical diffraction (see Paragraph [0126]).
As is clear from the simulation results, the light intensity distribution is widened as the proximity gap is increased. In Japanese Laid-Open Patent Publication No. 2007-072171, it is found that a smaller proximity gap is preferred from the viewpoint of exposure quality, and the proximity gap Lg of 50 μm is selected based on the finding.
However, in Japanese Laid-Open Patent Publication No. 2007-072171, though the simulation of proximity gap change within a range of 50 to 550 μm is performed to evaluate the light intensity distribution generated due to optical diffraction, when the conductive film is practically produced, the proximity gap is set to be 50 μm only, and not to a distance other than 50 μm.
In addition, the silver salt-type conductive film has a disadvantage of moire generation in a product.